Monday, August 24, 2015

In our last post, we studied the similarities and differences between the AR-15 and M16 trigger mechanisms. Today's post will be another educational movie courtesy of the US Army (your tax dollars at work!). We will study the methods of operating a M16 rifle and its functioning cycle.

Today's movie was produced sometime in the early 1960s and describes the operation of the M16 rifle, specifically the earlier models. It also shows the functioning cycle of operation of a M16 rifle (i.e.) Firing, Unlocking, Extracting, Ejecting, Cocking, Feeding, Chambering and Locking and describes in detail how each stage works.

Sunday, August 16, 2015

In today's post, we will look at a couple of videos that show the actual parts, instead of a 3-D Solidworks animation.

First up, an explanation of the AR-15 trigger mechanism:

Next, we have another video, that discusses the trigger mechanism of a M16 and compares it to that of an AR-15

Note that the M16 trigger mechanism being discussed is the M16-A1 model, which is capable of firing in semi-auto (single shot) and full-auto modes (unlike the M16-A2 and A4 models, which can fire in semi-auto and 3-round burst modes only). The AR-15 is capable of semi-auto fire only.

Saturday, August 8, 2015

In our last post, we saw a video that showed the basics of a bolt-action firearm, A bolt action is in the class of manually operated firearm actions. In today's post, we will study a few different classes of firearm actions, which we have already studied the basics of many months ago.

In the above links, we studied these actions using some illustrations and also studied some specific variations of these actions (e.g.) short recoil action, long recoil action, direct gas impingment, short stroke gas operation etc. We also studied examples of weapons that used these different actions.

Thanks to the efforts of the US Army, we actually have a movie that illustrates the basics of all of these actions.

Wednesday, August 5, 2015

In our last couple of posts, we saw a couple of examples of semi-automatic, full automatic and three round burst mechanisms. The first video was prepared by the US Army to train soldiers. As it turns out, the Army had actually prepared a set of videos. The first in the series showed an example of a bolt-action firearm in action. We will study that video in today's post:

In today's post, we will study another mode of firing: burst mode. Burst mode is an intermediate between semi-automatic and full automatic firing modes. In semi-automatic mode, the weapon will fire one round per trigger pull and the user has to release and pull the trigger again to fire the next shot. In full automatic mode, the weapon will continue to fire automatically as long as the trigger is held down and there is ammunition available in the magazine. While full automatic firing provides a lot more firepower than firing in semi-automatic mode, it also tends to waste a lot more ammunition, especially if soldiers are inexperienced and hold down on the trigger for longer than necessary. The recoil from firing in full automatic mode also leads to inaccuracies. Burst mode provides a compromise between these two firing modes. When a firearm selector is set to fire in burst mode, it will fire up to a set number of rounds (usually 2 or 3 rounds) per trigger pull. After that, the user has to release and pull the trigger again to fire the next set of rounds and so on.

In Vietnam, the US military found that new soldiers often ran out of ammunition in combat, because they had set their M16 rifles in full automatic mode and shot their entire supply of ammunition in a few seconds (and often without hitting their targets). Therefore, they requested that the M16A2 model remove the full automatic mode option and implement a burst mode instead. Their studies showed that a three-round burst provides the best balance between firepower, accuracy and conservation of ammunition. This is why the M16A2 and M16A4 models and the M4 carbine models have a three-round burst mode.

A person named "Stealth the Unknown" has prepared a great video showing how these different firing modes were implemented on the M16 family of rifles:

In the case of M16 models, the burst mode is implemented by a rotating cam. The same video also describes how the mechanism works for semi-automatic and full automatic modes.

The same author also prepared a second video answering some follow-up questions about this mechanism.

For instance, in a M16, if the user releases the trigger before a three round burst is complete, then the next trigger pull will only fire 1 or 2 rounds. This is because the M16's cam mechanism does not reset when the trigger is released. In some other firearms, the mechanism resets every time the trigger is released and therefore the next trigger pull will fire the full number of rounds. The author of the video also goes into an interesting theoretical design where he designed a selector with multiple burst firing modes as well as a semi-automatic and full automatic modes.

Saturday, August 1, 2015

Hello everyone, I'm back from my long vacation and it was simply awesome. I'll publish some pictures of firearms that I took while I was visiting various places in Europe in a few days, after I do some editing. Until that happens, let's study how various firing mechanisms work, with the aid of some movies.

In today's post, we will look at an interesting movie about how semi-automatic and fully automatic weapons work. This movie was prepared by the US Army for training purposes sometime around the World War II period.

Note that this film depicts one way to achieve semi-automatic and fully-automatic fire. There are also other mechanisms, which we will study in subsequent posts.